Drive assemblies for variable torque distribution normally include a differential with one input shaft and two output shafts which have a compensating effect relative to one another. The drive assembly for the variable transmission of torque functions in that, prior to being distributed to the two output shafts, part of the torque introduced via the input shaft is branched off the differential carrier. The branched-off percentage of torque is additionally introduced into one of the two output shafts following the branching-off point for the remaining torque. For this purpose, there is provided a transmission stage and a coupling per output shaft. The transmission stage includes an input gear which is driven by the differential carrier and which accelerates or decelerates an output gear. By coupling the output gear to the associated output shaft of the differential, the associated output shaft is accelerated or decelerated. In this way, it is possible, if required, for a greater amount of torque to be transmitted to the one of the two output shafts than to the other one of the output shafts in order to increase the driving stability of the motor vehicle. Such drive assemblies can be used for distributing torque between the two sideshafts of an axle differential or for the controlled distribution of torque between the two axle shafts of a central differential of a motor vehicle driven by several axles.
U.S. Pat. No. 6,056,660 describes a transmission stage for a drive assembly to achieve a variable torque distribution between two sideshafts of a driven axle. The transmission stage is provided in the form of an epicyclic transmission and comprises a plurality of planetary gears which are rotatably supported in a carrier element rotating in the differential housing. The planetary gears are connected in a rotationally fast way by means of a first toothed portion to the differential carrier and, by means of a sun gear, they are drivingly connected to the sideshaft. Per sideshaft, there is provided a multi-plate coupling which serves to brake a rotational movement of the respective carrier element relative to the differential housing. In this way, an additional torque is applied to the respective sideshaft.
U.S. Pat. No. 5,497,845 proposes a transmission stage for a drive assembly to permit a variable torque distribution between two sideshafts of a driven axle. This transmission stage is provided in the form of a stationary transmission and includes a layshaft which is rotatably supported in the transmission housing and comprises a plurality of toothed portions. One of the toothed portions is drivingly connected to the differential carrier, whereas another toothed portion is drivingly connected to a plate carrier element of a multi-plate coupling. The transmission ratio of the two toothed portions is such that the plate carrier element of the multi-plate coupling rotates faster than the associated sideshaft. Thus, by actuating the multi-plate coupling, an increased torque can be transmitted to the sideshaft.
U.S. Pat. No. 4,986,800 describes a four-wheel locking system for a motor vehicle. It includes a planetary drive with a plurality of planetary gears which engage an input sun gear and an output sun gear with different numbers of teeth. The speed change between the two sun gears is achieved by a profile displacement of the sets of teeth.
These assemblies are complex and present assembly difficulties. It would be desirable to provide simply designed, easy-to-produce drive assembly to achieve a variable distribution of torque.